基于农户调查的农用地流转影响因素研究——以重庆市典型区(县)为例

农用地流转是充分发挥土地利用效益,实现农业规模化生产和产业化经营的一种积极探索,采用参与式农户评估法,以重庆市典型区(县)为例,对农用地流转的影响因素进行了探讨。分析结果表明:缺乏规范的操作程序与农用地流转中介组织、缺乏完善的社会保障体系以及区位条件的差异是影响重庆地区农用地流转的主要因素。建立健全农用地流转相关政策和农村社会保障制度,加速城镇化进程和加强农村基础设施建设对重庆地区的农用地流转具有积极的推动作用。     

The importance of considering multiple interacting species for conservation of species at risk

Conservation of species at risk of extinction is complex and multifaceted. However, mitigation strategies are typically narrow in scope, an artifact of conservation research that is often limited to a single species or stressor. Knowledge of an entire community of strongly interacting species would greatly enhance the comprehensiveness and effectiveness of conservation decisions. We investigated how camera trapping and spatial count models, an extension of spatial-recapture models for unmarked populations, can accomplish this through a case study of threatened boreal woodland caribou (Rangifer tarandus caribou). Population declines in caribou are precipitous and well documented, but recovery strategies focus heavily on control of wolves (Canis lupus) and pay less attention to other known predators and apparent competitors. Obtaining necessary data on multispecies densities has been difficult. We used spatial count models to concurrently estimate densities of caribou, their predators (wolf, black bear [Ursus americanus], and coyote [Canis latrans]), and alternative prey (moose [Alces alces] and white-tailed deer [Odocoileus virginianus]) from a camera-trap array in a highly disturbed landscape within northern Alberta's Oil Sands Region. Median densities were 0.22 caribous (95% Bayesian credible interval [BCI] = 0.08–0.65), 0.77 wolves (95% BCI = 0.26–2.67), 2.39 moose (95% BCI = 0.56–7.00), 2.64 coyotes (95% BCI = 0.45–6.68), and 3.63 black bears (95% BCI = 1.25–8.52) per 100 km². (The white-tailed deer model did not converge.) Although wolf densities were higher than densities recommended for caribou conservation, we suggest the markedly higher black bear and coyote densities may be of greater concern, especially if government wolf control further releases these species. Caribou conservation with a singular focus on wolf control may leave caribou vulnerable to other predators. We recommend a broader focus on the interacting species within a community when conserving species.     

Hydraulic modeling of mussel habitat at a bridge-replacement site, Allegheny River, Pennsylvania, USA

The Allegheny River in Pennsylvania supports a large and diverse freshwater-mussel community, including two federally listed endangered species, Pleurobema clava (Clubshell) and Epioblasma torulosa rangiana (Northern Riffleshell). It is recognized that river hydraulics and morphology play important roles in mussel distribution. To assess the hydraulic influences of bridge replacement on mussel habitat, metrics such as depth, velocity, and their derivatives (shear stress, Froude number) were collected or computed.The objectives of the project were to evaluate mussel and hydraulic data at a reference site and to compare those findings to a bridge-replacement site. The findings were used to support a statistical analysis, which establishes correlations between mussel count and hydraulics, and a numerical model to forecast habitat based on the statistics.ArcGIS was selected to manage the data and generate a grid to compute area statistics for 3319, 4.9-m × 4.9-m cells (cell) for total mussel count, depth, velocity, shear stress, and Froude number. The Wilcoxon Rank Sum test indicated no statistical significance between the total mussel count and the hydraulic variables; however, trellis graphs were used to account for the spatial variability in the data set. For the flow conditions measured, the total mussel count per cell is greatest at sections where (1) velocities range from 0.061 to 0.21 m/s, (2) shear stresses range from 0.48 to 3.8 dyne/cm², and (3) Froude numbers range from 0.006 to 0.04.Based on the statistical targets established, the hydraulic model results suggest that an additional 2428 m² or a 30-percent increase in suitable mussel habitat could be generated at the replacement-bridge site when compared to the baseline condition associated with the existing bridge at that same location. The study did not address the influences of substrate, acid mine drainage, sediment loads from tributaries, and surface-water/ground-water exchange on mussel habitat. Future studies could include methods for quantifying (1) channel-substrate composition and distribution using tools such as hydroacoustic echosounders specifically designed and calibrated to identify bed composition and mussel populations, (2) surface-water and ground-water interactions, and (3) a high-streamflow event.     

Ninety five percent: an evaluation of law, policy, and programs to promote seat belt use in Washington state

Seat belt use in Washington state was 83% in 2001. In 2002, a series of law, policy, and program initiatives coalesced to produce a dramatic increase in seat belt use. Washington enacted a primary enforcement seat belt, the Chief of the Washington State Patrol made safety belt enforcement one of the core missions of that agency, and Washington participated in the national Memorial Day Click It or Ticket program during May 2002 and continued the program into 2003. Evaluation of these initiatives was accomplished through observation surveys of seat belt use, analysis of seat belt violation data, and analysis of data on traffic deaths of motor vehicle occupants. The major findings were that there was a two- to three-fold increase in enforcement of the seat belt law, belt use rates increased to 93% in 2002 and again to 95% in 2003, and motor-vehicle occupant fatalities decreased by 13%. IMPACT ON PRACTICE AND POLICY: The primary seat belt law and Click It or Ticket program activities were critical factors in increasing belt use in Washington state. Media and enforcement programs targeting seat belt use can be very effective in raising the belt use rate, but a long-term commitment to continuation of these program activities is essential. Other states implementing new primary seat belt laws should consider delivering a Click It or Ticket campaign prior to the effective date of the primary law and continuing these activities during subsequent months and years.     

ASSESSING THE ACCURACY OF PALEOHYDROLOGIC INDICATORS,HARPERS FERRY,WEST VIRGINIA1

ABSTRACT: Gaging stations established in 1895 at Millville, West Virginia and in 1882 at Harpers Ferry, West Virginia record flows ranging from a maximum of 6,509 m³s^-1 to a minimum of 2 m³s^-1. Historical and botanical indicators were used to extend the systematic flood record of the Shenandoah River for a study reach approximately 7.5-km long. The long systematic record at the site provides a good opportunity to assess the accuracy of these sources of paleoflood information. Habitation of the area by settlers of European descent began in 1733, and historical flood records extend from 1748. Qualitative historical records from different sources were compared to yield the most complete flood history. The correlation between the various sources was extremely high. Botanical flood evidence preserved as adventitious sprouts, tree scars, and ring anomalies were documented in 37 trees. A flood chronology established from these data extended from 1896 to 1955. Botanical indicators provided an accurate, although incomplete, flood chronology. The ability to determine accurate flood stages from paleohydrologic indicators varied. Historical data yielded relatively accurate stages to within 1–2 m; only minimum values of flood stage could be obtained from botanical indicators. These results illustrate some of the strengths and weaknesses of paleohydrologic investigations in the eastern United States.     

NETWORK DESIGN FOR WATER SUPPLY FORECASTING IN THE WEST1

ABSTRACT: The objective is to develop techniques to evaluate how changes in basic data networks can improve accuracy of water supply forecasts for mountainous areas. The approach used was to first quantify how additional data would improve our knowledge of winter precipitation, and second to estimate how this knowledge translates, quantitatively, into improvement in forecast accuracy. A software system called DATANET was developed to analyze each specific gage network alternative. This system sets up a fine mesh of grid points over the basin. The long-term winter mean precipitation at each grid point is estimated using a simple atmospheric model of the orographic precipitation process. The mean runoff at each grid point is computed from the long-term mean precipitation estimate. The basic runoff model is calibrated to produce the observed long-term runoff. The error analysis is accomplished by comparing the error in forecasts based on the best possible estimate of precipitation using all available data with the error in the forecasts based on the best possible estimate of winter precipitation using only the gaged data. Different data network configurations of gage sites can be compared in terms of forecast errors.     

THE STATUS OF NONPOINT SOURCE POLLUTION: ITS NATURE,EXTENT AND CONTROL1

Nonpoint source pollution remains as the primary reason for the designation of many of the Nation's streams as “water quality limited.” This means that even with the application of technology-based effluent limitations on point sources, ambient water quality standards will not be met. This paper explores several of the reasons why nonpoint sources are so difficult to come to grips with. These reasons include: (1) the inability to expand the definition of nonpoint sources to encompass nonengineering attributes, (2) the relatively primitive state of characterizing nonpoint sources, (3) the lack of prior success in conducting programs to study and alleviate nonpoint problems, and (4) an uncertain approach to providing incentives for control practices.     

九宫山自然保护区功能模糊综合评价

功能评价是保护区改善管理以实现保护区最佳功能的有效手段。运用模糊数学理论和问卷调查方法,建立3层20个指标的评价体系,对九宫山自然保护区的功能进行模糊综合评价和贴近度分析。结果显示,保护区自然保护和社会发展功能评价为“好”,宣传教育、科学研究和经济发展功能评价为“一般”,因而整体功能状况评价为“好”。贴近度分析表明,改善保护区功能要从资源与景观的保护、宣传教育设施、宣传教育手段、科研基础条件、科研合作与影响、对外交流、人口素质和保护区经济效益等方面着手。提出了从加强资源与景观的保护、加强宣传教育、加强和改善科学研究、提高保护区周边人口的素质和提高保护区的经济效益等方面改善管理的一系列具体建议,以实现保护区的最佳功能。     

Survey methods for assessing land cover map accuracy

The increasing availability of digital photographic materials has fueled efforts by agencies and organizations to generate land cover maps for states, regions, and the United States as a whole. Regardless of the information sources and classification methods used, land cover maps are subject to numerous sources of error. In order to understand the quality of the information contained in these maps, it is desirable to generate statistically valid estimates of accuracy rates describing misclassification errors. We explored a full sample survey framework for creating accuracy assessment study designs that balance statistical and operational considerations in relation to study objectives for a regional assessment of GAP land cover maps. We focused not only on appropriate sample designs and estimation approaches, but on aspects of the data collection process, such as gaining cooperation of land owners and using pixel clusters as an observation unit. The approach was tested in a pilot study to assess the accuracy of Iowa GAP land cover maps. A stratified two-stage cluster sampling design addressed sample size requirements for land covers and the need for geographic spread while minimizing operational effort. Recruitment methods used for private land owners yielded high response rates, minimizing a source of nonresponse error. Collecting data for a 9-pixel cluster centered on the sampled pixel was simple to implement, and provided better information on rarer vegetation classes as well as substantial gains in precision relative to observing data at a single-pixel.     

植物源杀虫剂川楝素对环境生物安全性评价

评价农药对环境中非靶标生物的毒性是新农药开发应用的重要环节.依据国家环境保护局"化学农药环境安全评价试验准则",测定了78%川楝素原粉和0.5%川楝素乳油对生态环境中非靶标生物的毒性,并进行了安全性评价.结果表明,川楝素原粉对鹌鹑、家蚕、蜜蜂、蚯蚓、瓢虫、蝌蚪等非靶标生物均为低毒;川楝素乳油对家蚕、蜜蜂、蚯蚓、瓢虫等均为低毒,对家蚕的生长发育具有一定的影响,对鹌鹑中毒,对蝌蚪高毒.可见,植物源杀虫剂川楝素对环境非靶标生物毒性低、较为安全,但在水田及桑园应慎用0.5%川楝素乳油.